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Ultrasound velocimetry has been widely used for blood flow imaging. However, the flow measurements are constrained to resolve the in‐plane 2D flow components when using a 1D transducer array. In this work, an ultrasound speckle decorrelation analysis‐based velocimetry (3C‐vUS) is proposed for 3D velocity components measurement using a 1D transducer array. The 3C‐vUS theory is first derived and validated with numerical simulations and phantom experiments. The in vivo testing results show that 3C‐vUS can accurately measure the blood flow 3D‐velocity‐components of the human carotid artery at arbitrary probe‐to‐vessel angles throughout the cardiac cycle. With such capability, the 3C‐vUS will alleviate the requirement of operators and promote disease screening for blood flow‐related disorders. [ABSTRACT FROM AUTHOR]

Abstract Ultrasound velocimetry has been widely used for blood flow imaging. However, the flow measurements are constrained to resolve the in‐plane 2D flow components when using a 1D transducer array. In this work, an ultrasound speckle decorrelation analysis‐based velocimetry (3C‐vUS) is proposed for 3D velocity components measurement using a 1D transducer array. The 3C‐vUS theory is first derived and validated with numerical simulations and phantom experiments. The in vivo testing results show that 3C‐vUS can accurately measure the blood flow 3D‐velocity‐components of the human carotid artery at arbitrary probe‐to‐vessel angles throughout the cardiac cycle. With such capability, the 3C‐vUS will alleviate the requirement of operators and promote disease screening for blood flow‐related disorders.

Objective: Helical stents have been developed to treat peripheral arterial disease (PAD) in the superficial femoral artery (SFA), with the premise that their particular geometry could promote swirling flow in the blood. The aim of this work is to provide evidence on the existence of this swirling flow by quantifying its signatures., Materials and Methods: This study consists of in vitro and in vivo parts. For the in vitro part, 3 helical stent models of different helicity degrees and 1 straight model were fabricated, and the flow was assessed at the inlet and outlet of each model. For the in vivo part, only 1 patient, treated with the helical stent, was eligible to participate in the study. The stent implanted in the SFA of the patient was evaluated in 2 leg postures (straight and flexed), and flow was assessed in 12 locations along the SFA. The in vivo study was approved by an ethical board (NL80130.091.21) in the Netherlands. High-frame-rate ultrasound was used to acquire data from the regions of interest (ROIs), using microbubbles as contrast agents. After processing the data via a correlation-based algorithm (echo particle image velocimetry or echoPIV), the velocity vector field within each ROI was extracted and analyzed for parameters such as vector complexity and velocity profile skewedness., Results: The results show that in the outlet of the helical stents, when compared with the inlet, the flow vector field is more complex and the velocity profile is more skewed. For the in vivo case, the outcomes demonstrate more complexity and higher variability in the sign of skewedness inside the stent when compared with the flow in the proximal to the stent., Conclusions: Helical stents make the vector field of the flow more complex and the velocity profile more skewed, both of which are signatures of swirling flow. Further studies are needed to evaluate whether these features can benefit patients in terms of patency rates., Clinical Impact: This study demonstrates that helical stent models alter the blood flow when compared with straight stent models. Particularly, the flow grows more complex and its velocity profile becomes more skewed, both of which hint at the existence of swirling flow inside the helical stent. These observations, alongside with population-based studies that are currently being carried out, may provide the evidence that helical stents have some advantages over straight stents for the patients., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

High-frame-rate (HFR) echo-particle image velocimetry (echoPIV) is a promising tool for measuring intracardiac blood flow dynamics. In this study, we investigate the optimal ultrasound contrast agent (UCA: SonoVue) infusion rate and acoustic output to use for HFR echoPIV (PRF = 4900 Hz) in the left ventricle (LV) of patients. Three infusion rates (0.3, 0.6, and 1.2 ml/min) and five acoustic output amplitudes (by varying transmit voltage: 5, 10, 15, 20, and 30 V—corresponding to mechanical indices of 0.01, 0.02, 0.03, 0.04, and 0.06 at 60-mm depth) were tested in 20 patients admitted for symptoms of heart failure. We assess the accuracy of HFR echoPIV against pulsed-wave Doppler acquisitions obtained for mitral inflow and aortic outflow. In terms of image quality, the 1.2-ml/min infusion rate provided the highest contrast-to-background ratio (CBR) (3-dB improvement over 0.3 ml/min). The highest acoustic output tested resulted in the lowest CBR. Increased acoustic output also resulted in increased microbubble disruption. For the echoPIV results, the 1.2-ml/min infusion rate provided the best vector quality and accuracy; mid-range acoustic outputs (corresponding to 15–20-V transmit voltages) provided the best agreement with the pulsed-wave Doppler. Overall, the highest infusion rate (1.2 ml/min) and mid-range acoustic output amplitudes provided the best image quality and echoPIV results. [ABSTRACT FROM AUTHOR]

Ultrasound velocity was measured in hyaluronan solutions of various compositions at different temperatures. The velocity dependence on hyaluronan concentration at constant temperature (25 °C) was linear both in water and in 0.15 M NaCl regardless of hyaluronan molecular weight, confirming diluted-solution behavior. During cyclic heating and cooling, hysteresis on the temperature dependence of ultrasound velocity was observed in the range 30–55 °C in aqueous solutions for all molecular weights. In NaCl solutions, the hysteresis was suppressed and, in contrast to solutions in water where the velocity demonstrated a local maximum with temperature, the velocity decreased with increasing temperature. These findings were attributed to slow and hydration-linked hyaluronan conformation transitions during cooling in water, which were suppressed by the presence of salt, which makes hyaluronan's coiled conformation more compact. [ABSTRACT FROM AUTHOR]

In rock grouting, idealized 2D-radial laminar flow of yield stress fluids (YSF) is a fundamental flow configuration that is used for cement grout spread estimation. A limited amount of works have presented analytical and numerical solutions on the radial velocity profiles between parallel disks. However, to the best of our knowledge, there has been no experimental work that has presented measured velocity profiles for this geometry. In this paper, we present velocity profiles of Carbopol (a simple YSF), measured by pulsed ultrasound velocimetry within a radial flow model. We describe the design of the physical model and then present the measured velocity profiles while highlighting the plug-flow region and slip effects observed for three different apertures and volumetric flow rates. Although the measured velocity profiles exhibited wall slip, there was a reasonably good agreement with the analytical solution. We then discuss the major implications of our work on radial flow. [ABSTRACT FROM AUTHOR]

Investigations of ventricular flow patterns during mechanical circulatory support are limited to in vitro flow models or in silico simulations, which cannot fully replicate the complex anatomy and contraction of the heart. Therefore, the feasibility of using echocardiographic particle image velocimetry (Echo-PIV) was evaluated in an isolated working heart setup. Porcine hearts were connected to an isolated, working heart setup and a left ventricular assist device (LVAD) was implanted. During different levels of LVAD support (unsupported, partial support, full support), microbubbles were injected and echocardiographic images were acquired. Iterative PIV algorithms were applied to calculate flow fields. The isolated heart setup allowed different hemodynamic situations. In the unsupported heart, diastolic intra-ventricular blood flow was redirected at the heart's apex towards the left ventricular outflow tract (LVOT). With increasing pump speed, large vortex formation was suppressed, and blood flow from the mitral valve directly entered the pump cannula. The maximum velocities in the LVOT were significantly reduced with increasing support. For the first time, cardiac blood flow patterns during LVAD support were visualized and quantified in an ex vivo model using Echo-PIV. The results reveal potential regions of stagnation in the LVOT and, in future the methods might be also used in clinical routine to evaluate intraventricular flow fields during LVAD support. [ABSTRACT FROM AUTHOR]

The characteristics of the flows of boluses with different consistencies, i.e. different rheological properties, through the pharynx have not been fully elucidated. The results obtained using a novel in vitro device, the Gothenburg Throat, which allows simultaneous bolus flow visualisation and manometry assessments in the pharynx geometry, are presented, to explain the dependence of bolus flow on bolus consistency. Four different bolus consistencies of a commercial food thickener, 0.5, 1, 1.5 and 2 Pa s (at a shear rate of 50 s-1)-corresponding to a range from low honey-thick to pudding-thick consistencies on the National Dysphagia Diet (NDD) scale-were examined in the in vitro pharynx. The bolus velocities recorded in the simulator pharynx were in the range of 0.046-0.48 m/s, which is within the range reported in clinical studies. The corresponding wall shear rates associated with these velocities ranged from 13 s-1 (pudding consistency) to 209 s-1 (honey-thick consistency). The results of the in vitro manometry tests using different consistencies and bolus volumes were rather similar to those obtained in clinical studies. The in vitro device used in this study appears to be a valuable tool for pre-clinical analyses of thickened fluids. Furthermore, the results show that it is desirable to consider a broad range of shear rates when assessing the suitability of a certain consistency for swallowing. [ABSTRACT FROM AUTHOR]

Accurate measurement of blood flow velocity is important for the prevention and early diagnosis of atherosclerosis. However, due to the uncertainty of parameter settings, the autocorrelation velocimetry methods based on clutter filtering are prone to incorrectly filter out the near-wall blood flow signal, resulting in poor velocimetric accuracy. In addition, the Doppler coherent compounding acts as a low-pass filter, which also leads to low values of blood flow velocity estimated by the above methods. Motivated by this status quo, here we propose a deep learning estimator that combines clutter filtering and blood flow velocimetry based on the adaptive property of one-dimensional convolutional neural network (1DCNN). The estimator is operated by first extracting the blood flow signal from the original Doppler echo signal through an affine transformation of the 1D convolution, and then converting the extracted signal into the desired blood flow velocity using a linear transformation function. The effectiveness of the proposed method is verified by simulation as well as in vivo carotid artery data. Compared with typical velocimetry methods such as high-pass filtering (HPF) and singular value decomposition (SVD), the results show that the normalized root means square error (NRMSE) obtained by 1DCNN is reduced by 54.99 % and 53.50 % for forward blood flow velocimetry, and 70.99 % and 69.50 % for reverse blood flow velocimetry, respectively. Consistently, the in vivo measurements demonstrate that the goodness-of-fit of the proposed estimator is improved by 8.72 % and 4.74 % for five subjects. Moreover, the estimation time consumed by 1DCNN is greatly reduced, which costs only 2.91 % of the time of HPF and 12.83 % of the time of SVD. In conclusion, the proposed estimator is a better alternative to the current blood flow velocimetry, and is capable of providing more accurate diagnosis information for vascular diseases in clinical applications. • Integrates clutter filtering and blood flow velocimetry into a single neural network model • Can be applied directly to Doppler echo signals without IQ demodulation • Uses the Field II platform to generate data to train the model • Corrects for low blood flow velocity caused by coherent compounding • Outperforms advanced clutter filtering-based blood flow velocity estimators [ABSTRACT FROM AUTHOR]

Abstract: Ferrofluid spin-up flow is studied within a sphere subjected to a uniform rotating magnetic field from two surrounding spherical coils carrying sinusoidally varying currents at right angles and 90° phase difference. Ultrasound velocimetry measurements in a full sphere of ferrofluid shows no measureable flow. There is significant bulk flow in a partially filled sphere (1–14mm/s) of ferrofluid or a finite height cylinder of ferrofluid with no cover (1–4mm/s) placed in the spherical coil apparatus. The flow is due to free surface effects and the non-uniform magnetic field associated with the shape demagnetizing effects. Flow is also observed in the fully filled ferrofluid sphere (1–20mm/s) when the field is made non-uniform by adding a permanent magnet or a DC or AC excited small solenoidal coil. This confirms that a non-uniform magnetic field or a non-uniform distribution of magnetization due to a non-uniform magnetic field are causes of spin-up flow in ferrofluids with no free surface, while tangential magnetic surface stress contributes to flow in the presence of a free surface. Recent work has fitted velocity flow measurements of ferrofluid filled finite height cylinders with no free surface, subjected to uniform rotating magnetic fields, neglecting the container shape effects which cause non-uniform demagnetizing fields, and resulting in much larger non-physical effective values of spin viscosity η′∼10−8−10−12 Ns than those obtained from theoretical spin diffusion analysis where η′≤10−18 Ns. COMSOL Multiphysics finite element computer simulations of spherical geometry in a uniform rotating magnetic field using non-physically large experimental fit values of spin viscosity η′∼10−8−10−12 Ns with a zero spin-velocity boundary condition at the outer wall predicts measureable flow, while simulations setting spin viscosity to zero (η′=0) results in negligible flow, in agreement with the ultrasound velocimetry measurements. COMSOL simulations also confirm that a non-uniform rotating magnetic field or a uniform rotating magnetic field with a non-uniform distribution of magnetization due to an external magnet or a current carrying coil can drive a measureable flow in an infinitely long ferrofluid cylinder with zero spin viscosity (η′=0). [Copyright &y& Elsevier]

Abstract: We applied precise densimetry and ultrasound velocimetry methods to study the interaction of a synthetic α-helical transmembrane peptide, acetyl-K2-L24-K2-amide (L24), with model bilayer lipid membranes. The large unilamellar vesicles (LUVs) utilized were composed of a homologous series of n-saturated diacylphosphatidylcholines (PCs). PCs whose hydrocarbon chains contained from 13 to 16 carbon atoms, thus producing phospholipid bilayers of different thicknesses and gel to liquid-crystalline phase transition temperatures. This allowed us to analyze how the difference between the hydrophobic length of the peptide and the hydrophobic thickness of the lipid bilayer influences the thermodynamical and mechanical properties of the membranes. We showed that the incorporation of L24 decreases the temperature and cooperativity of the main phase transition of all LUVs studied. The presence of L24 in the bilayer also caused an increase of the specific volume and of the volume compressibility in the gel state bilayers. In the liquid crystalline state, the peptide decreases the specific volume at relatively higher peptide concentration (mole ratio L24:PC=1:50). The overall volume compressibility of the peptide-containing lipid bilayers in the liquid-crystalline state was in general higher in comparison with pure membranes. There was, however, a tendency for the volume compressibility of these lipid bilayers to decrease with higher peptide content in comparison with bilayers of lower peptide concentration. For one lipid composition, we also compared the thermodynamical and mechanical properties of LUVs and large multilamellar vesicles (MLVs) with and without L24. As expected, a higher cooperativity of the changes of the thermodynamical and mechanical parameters took place for MLVs in comparison with LUVs. These results are in agreement with previously reported DSC and 2H NMR spectroscopy study of the interaction of the L24 and structurally related peptides with phosphatidylcholine bilayers. An apparent discrepancy between 2H NMR spectroscopy and compressibility data in the liquid crystalline state may be connected with the complex and anisotropic nature of macroscopic mechanical properties of the membranes. The observed changes in membrane mechanical properties induced by the presence of L24 suggest that around each peptide a distorted region exists that involves at least 2 layers of lipid molecules. [Copyright &y& Elsevier]

19-mer oligonucleotides with oleylamine tethered at 3′ and 5′ terminal, respectively, were incorporated into unilamellar liposomes of dioleoylphosphatidylcholine (DOPC). Addition of complementary nucleotide resulted in hybridization with oligonucleotides located on different liposomes and caused liposome aggregation. Significant changes of sound velocimetry and turbidity were readily observed at 10 nM concentration of the complementary chain. [Copyright &y& Elsevier]

• 1-hydroxy and 1,3,6-hydroxy-xanthones decrease compressibility of PCs membranes. • The fluidity of the phosphatidylcholine membranes increases with hydroxy-xanthones. •Fluidity and compressibility were analyzed with experimental and computational methods. This work reports the effect of hydroxy-xanthones (XAs) on 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers as determined by ultrasound velocimetry, densimetry and molecular dynamics simulations. XAs with different number of hydroxyl group were studied. Experimental results, in good agreement with molecular dynamics simulations, revealed that the presence of XAs in the systems studied increases fluidity while simultaneously decreses the compressibility of both membranes. This ´apparent contradiction´ ceases to exist when the particular geometrical structure of the xanthones is taken into account: the planar shape of their fused aromatic rings might allow them to pack efficiently among the hydrocarbon tails of the lipids, thus decreasing compressibility, while their presence weakens or disrupts methylene-methylene interchain interactions, thus increasing membrane fluidity and decreasing their melting temperature. [ABSTRACT FROM AUTHOR]

In this work, we performed targeted immobilization of immunoglobulins by means of bacterial S-layer proteins from Bacillus coagulans E38-66/V1 recrystallized on liposomes, which were exploited as immobilization matrix for antibody (Ab)-human IgG. The study of interaction of rabbit or swine anti-human IgG as antigens (Ag) was performed by means of measuring changes of ultrasound velocity. We showed that at a temperature of 25 °C, the increment of ultrasound velocity [u] linearly decreased following an increase of concentration of Ag. The decrease of [u] was presumably due to changes of hydration of the membrane due to the binding process. Approximately 10 times lower changes of [u] were observed at 45 °C for Ag–Ab interaction as well as for nonspecific interaction of Ag with liposomes covered by S-layer without Ab. No substantial differences in the behaviour of [u] were observed for interactions of human IgG with rabbit or swine anti-human IgG. [Copyright &y& Elsevier]